package org.checkerframework.checker.index.qual;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.checkerframework.framework.qual.JavaExpression;
import org.checkerframework.framework.qual.SubtypeOf;

/**
 * An annotation indicating the relationship between values with a byte, short, char, int, or long
 * type.
 *
 * <p>If an expression's type has this annotation, then at run time, the expression evaluates to a
 * value that is less than the value of the expression in the annotation.
 *
 * <p>{@code @LessThan("end + 1")} is equivalent to {@code @LessThanOrEqual("end")}.
 *
 * <p>Subtyping:
 *
 * <ul>
 *   <li>{@code @LessThan({"a", "b"}) <: @LessThan({"a"})}
 *   <li>{@code @LessThan({"a", "b"})} is not related to {@code @LessThan({"a", "c"})}.
 * </ul>
 */
@SubtypeOf({LessThanUnknown.class})
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE_PARAMETER, ElementType.TYPE_USE})
// TODO: I chose to implement less than rather than greater than because in most of the case studies
// false positives, the bigger value is final or effectively final, so it can appear in a dependent
// annotation without causing soundness issues.
public @interface LessThan {
    /**
     * The annotated expression's value is less than this expression.
     *
     * <p>The expressions in {@code value} may be addition/subtraction of any number of Java
     * expressions. For example, {@code @LessThan(value = "x + y + 2"}}.
     *
     * <p>The expression in {@code value} must be final or constant or the addition/subtract of
     * final or constant expressions.
     */
    @JavaExpression
    String[] value();
}
